I'm connected to an Alcatel v1 DSLAM which is situated some 6.5Km away. Attenuation @ 300KHz is around 84dB. The only two routers that will sync are the Netgear DG834G v3 (not v4, GT, v5) and the 2 Wire 2700HGV. Of the two the 2wire sync at around 896kbps as opposed to 608 with the Netgear. Hence I use the 2Wire (picked up on ebay.co.uk for £10 inc postage).
Other routers tried but which failed to sync are: Speedtouch ST585 v6, D-Link DSL 2640b and Sagem Livebox 2.
Please note that I live in France and FT do things differently to BT . So things that happen here may not happen over in the UK.
Hope this helps.
barrie